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Topic: Commercial Gouda press (Read 7012 times)

So in other words, you are saying that the compression of the cheeses being pressed in the near infinite line of molds would all be experiencing the same pressure?

Newton's first law, an object at rest tends to remain at rest...so when one applies pressure at one end of the line of cheese/molds regardless of the compression involved with the cheeses themselves, this pressure is distributed evenly throughout the near infinite line of molds/cheeses? Mind boggling lol

Something has always got to be pushing back. If I put 10 lbs of load on one side of something, if it's in equilibrium (not moving), then something is pushing back with 10 lbs.

In a vertical cheese press system, the load carried by the bottom cheese (assuming no load is transfer to the molds--which a good design would try to ensure) would be equal to the load applied to the top cheese plus the weight of each of the cheeses and molds on top.

In a horizontal system, you can introduce a little bit of complexity in the analysis if the molds are resting on something, but if they are suspended between the load applying end (a piston of some sort, perhaps) and the "base" such that those are the only two points in contact with the stack of cheeses, each cheese will experience the same force.

So, in the case of an infinitely long, horizontal stack of molds, if the molds are only touching one another, they will each be carrying the same load. If they are resting on the ground, the friction between each mold and the ground will lessen the load the next cheese carries until there is no longer any load applied to the cheeses. Example: 10 lbs of load is applied, cheese 1 experiences 10 lbs, but 1 lb of the reaction is provided not by the next cheese in line, but by friction with the ground. Cheese 2 expereiences 9 lbs, Cheese 3 8 lbs, etc.

Naturally though, the magnitude of the friction involved is highly dependent on the material the molds are resting on. If you have a very smooth surface, perhaps even lubricated, the friction involved starts to approach very small numbers. Also, if they are resting on something like two horizontal bars, two or three points of contact, that will dramatically reduce the friction involved. When I was thinking about this last night, I assumed the "chain" was resting on something very smooth so no weird gravitational effects would lead to tensions or bending of the chain. Personally, I have don't like hyperbolic trig functions (wink at Mike). I also assumed that since this discussion was about commercial presses, likely the cheeses involved were larger and thus involve much greater pressing forces (or load as you call it). In your case, lets assume each cheese assumes a friction equivalent to 1 lb. Lets suppose we are working with 7in diameter molds. Then the cross sectional surface area is about 38.34 in^2. If we want 4 PSI, then that means our piston must apply 153.37 lbs of force. Lets call it 160.So the first mold feels 160 lbs of force, the second 159, on to the nth cheese which feels 160 - (n-1). This means for 10 molds, the last cheese experiences 151 lbs. This is a difference of 9 lbs which is a percentage difference of 9/160 = 5.6%. Personally, I am not inclined to worry about consistency issues there. Of course I have made assumptions here, put into practice other variables could come into play.

I am kind of tempted to code up a model now and run some experiments... cheese is more fun when you geek out on it :p

Mike, two comments:1) You name seems vaugely familiar to me... You into any other hobbies or things where you use your name (if you don't mind my asking)2) What field are you in? Some flavor of engineering I assume?

I agree that the loss in load (and thus pressure) would be negligable in a horizontal press system, though it could be significant in a vertical system depending on the pressure needed, size of the wheels, and height of the stack.

I once participated in online apologetics, using the name Mike Richards, but have, to the delight of my wife, recovered from that addiction...

I've got a BS in Mechanical Engineering and an MS in Nuclear Engineering. I currently teach a course in Statics and Strength of Materials, should teach a first semester physics class next semester, and will be joining the Thermal Fluid Science team in the near future teaching Thermodynamics, Fluids, Heat Transfer, etc...(though I'll need to do a little dusting up on those topics before I get in front of a class).

B.S./M.S. Mathematics, Physics minor. I work as a software engineer though. When I was studying Physics, most of my elective upper division work was in particle physics.

Apologetics huh? My cousin used to be into Christian Apologetics. I think he got frustrated and quit though, I have so say that for someone with no formal training in logic/philosophy or debate many of his arguments were pretty dang clever! I like philosophy a lot but I am more into logic and epistemology. Metaphysics sometimes makes its way in but is not really a primary interest.

Something has always got to be pushing back. If I put 10 lbs of load on one side of something, if it's in equilibrium (not moving), then something is pushing back with 10 lbs.

So, in the case of an infinitely long, horizontal stack of molds, if the molds are only touching one another, they will each be carrying the same load. If they are resting on the ground, the friction between each mold and the ground will lessen the load the next cheese carries until there is no longer any load applied to the cheeses. Example: 10 lbs of load is applied, cheese 1 experiences 10 lbs, but 1 lb of the reaction is provided not by the next cheese in line, but by friction with the ground. Cheese 2 expereiences 9 lbs, Cheese 3 8 lbs, etc.

Naturally though, the magnitude of the friction involved is highly dependent on the material the molds are resting on. If you have a very smooth surface, perhaps even lubricated, the friction involved starts to approach very small numbers. Also, if they are resting on something like two horizontal bars, two or three points of contact, that will dramatically reduce the friction involved. When I was thinking about this last night, I assumed the "chain" was resting on something very smooth so no weird gravitational effects would lead to tensions or bending of the chain. Personally, I have don't like hyperbolic trig functions (wink at Mike). I also assumed that since this discussion was about commercial presses, likely the cheeses involved were larger and thus involve much greater pressing forces (or load as you call it). In your case, lets assume each cheese assumes a friction equivalent to 1 lb. Lets suppose we are working with 7in diameter molds. Then the cross sectional surface area is about 38.34 in^2. If we want 4 PSI, then that means our piston must apply 153.37 lbs of force. Lets call it 160.So the first mold feels 160 lbs of force, the second 159, on to the nth cheese which feels 160 - (n-1). This means for 10 molds, the last cheese experiences 151 lbs. This is a difference of 9 lbs which is a percentage difference of 9/160 = 5.6%. Personally, I am not inclined to worry about consistency issues there. Of course I have made assumptions here, put into practice other variables could come into play.

I am kind of tempted to code up a model now and run some experiments... cheese is more fun when you geek out on it :p

Actually...what is the byproduct of compression? Heat...Heat = energyAs you would add pressure, compressing the cheeses, a small amount of heat loss would result from the compression of each cheese. Long before you reached anything approaching infinity you would be left with something approaching zero pressure and zero compression being applied to the cheese.

The answer to the question related to a chain of cheese molds approaching infinity being pressed, what is the pressure being applied to the last forms in the chain is: Zero

Same thing applies to a series of springs...compression generates heat...heat equals loss of energy...

Energy is the ability to do work, and work requires movement ( W=FxX ). Once a static point is reached no more work is done. So once movement has stopped I think that only the reactive force of (static) friction affects the force pushing on each of the horizontal molds .

Energy is the ability to do work, and work requires movement ( W=FxX ). Once a static point is reached no more work is done. So once movement has stopped I think that only the reactive force of (static) friction affects the force pushing on each of the horizontal molds .

Si senior! Difficult to talk about dynamics when the system is not acting dynamically

I suppose if we include dynamic response, and drop the rigid body assumption (allow the cheeses to compress), then in an infinitely long set of cheeses, the "last" cheese would never feel the force applied to the first cheese. This, however, is primarily because in an infinitely long set of cheeses, the last cheese is infinitely far away and the force would simply never get to it. Additionally the mass of the system would be infinite, and what we think of as the inertia of the mass would provide the reaction force keeping the entire system in equilibrium even though there is no real reaction at the other "end" of the stack. What is more interesting, to me, is that in this same scenario, putting a small force on the "stack" of cheeses would squish the entire stack an infinite amount. I once pointed out in a class that I could make a beam of steel stretch more than 1 foot with my bare hands. Of course, the beam would have to be something like 2,000 miles long...but still, I'm like superman!

In a more realistic case, though, with less than an infinite number of cheeses, each individual cheese (in a horizontal press) needs to experience the same force on the front (top) of the cheese as it does on the back (bottom) of the cheese or it would be accelerating. I suppose that since the cheeses are compressing, the center of mass of the cheese-system is in fact moving away from the piston and towards the "base". Since this is true, and since the speed with which it is moving is not constant, it must be accelerating (technically, not necessarily going faster), which means the net force on the system must be non-zero. If the net force on the system is non-zero, then the net force on each individual cheese is also non-zero. Those cheeses near the piston are accelerating more than those near the base (think of the distance they each travel). Therefore, the cheeses are experiencing different forces and thus different pressures.

Once the cheeses stop compressing, the center of mass is no longer moving, and the net force across the entire system and within each cheese is zero, so they are all experiencing the same force and thus the same pressure. I guess, then, that everyone is right, depending on what part of the cheese pressing they were considering. Some might argued that cheeses are always compressing while in the press--I don't know if that's true, but I doubt it. It seems to me that they get to a point where they no longer compress under a given load.

And now you can agree with my students that I talk too much...and give details they don't really want: "Just teach us what we need to know for the test."

That is correct--contact area doesn't affect friction, it's simply the product of the normal force and the coefficient of friction (either static or kinetic). For most of us, this comes as counter-intuitive and usually requires us to just hit the "I believe" button and move on (this is one of those topics that I have never internalized as true, and just continually hit the "I believe" button). There are certain circumstances where surface area does matter (like when things are sticky...) to resistance forces (I'm not sure that we'd really call those friction, though).

Thanks for visiting Nerd city, by the way. I kind of figured this forum was a suburb of Nerd City--I mean, what kind of people really make cheese, anyway?

If you think of friction as if it is caused by the pressure between two surfaces then it becomes more intuitive. So then a contact area of 30 square inches is 30 times the area of a 1 square inch area , but the pressure is 1/30th so the friction force is the same for both.

I tried to skim all of the pertinent information out, but maybe I missed this. I don't think it has come up though.

Another factor we have is the slack present in each cheese. During the first several pressings, each of the cheeses is actually absorbing some of the energy being put into it. Otherwise the pressing would be doing nothing. The cheese is not merely a vessel through which the energy passes, the object of the pressing is to change the cheese, and this requires a certain amount of energy to accomplish. So some of our weight, instead of shooting straight through to the bottom, gets distracted in our cheese. This of course diminishes each time we press the cheese. But in a heavy press stack, I can notice more wehy fleeing from the top cheese than from the bottom (taking some of our energy with it)

A certain amount of the pressing weight is being used by each cheese to pack and rearrange the curd structure. Having pressed stacked cheeses before, experience tells me that position does make a big difference, and rotation is very important to getting consistent results.

You do need to factor your pressing weight for the size of your cheese. Some say PSI, I prefer to factor by mass. Because what if you factor your weight by the surface area of a cheese, but one is tall and the other is thin? The tall cheese will not press as well under the same weight as the thin one. Yes, a quick look at static physics should tell us that this shouldn't matter. But this assumes we are pressing a consistent gel, which we are not. We are pressing a large mass that has holes in it, pockets of liquid, and maybe even curd in various stages of dryness. factoring by weight accounts for the fact that a bigger mass of cheese is going to have more curd space to remove than a smaller one of the same diameter. It will either take more force (i.e. weight) or more time to press the bigger cheese with the same diameter as a smaller one effectively.

I factor pressing weight by the weight of the cheese to be pressed, and multiply by 8.

The discussion of the physics of the friction of the multiple horizontal molds has almost nothing to do with actual process of cheese making. It is only some physics nerds having fun. In cheese making , it's experience, experience,experience.